Process for printing with non-ferrous metal lithographic printing plates

ABSTRACT

Non-ferrous lithographic printing plates, and especially those in which the hydrophobic image areas are constituted by photosensitive solvent soluble polymers, are made hydrophilic in non-image areas by application to the metal surface of the developed plate a fountain solution of an aqueous desensitizing solution comprising a phosphate glass such as sodium hexametaphosphate, about 75 - 300 grams per 1,000 cc of water, in admixture with a fluoride salt, such as sodium fluoride of about 20 - 150 grams per 1,000 cc of water, the admixed aqueous composition may be maintained at a pH in the range of pH 7 by a water-soluble acid, such as phosphoric acid since control of the pH in the fountain solutions can be critical with recent innovations in ink manufacture. The treatment can be performed at room temperature and in addition to cleaning the plate the fountain solution assists in preserving the hydrophilic areas of the printing plate during storage without special protection. Preferably in a press fountain the solution is diluted within the range of 1 part solution to 30 - 60 parts water.

United States Patent [191 Harper May 6, 1975 PROCESS FOR PRINTING WITH NON-FERROUS METAL LITI-IOGRAPI-IIC PRINTING PLATES [76] Inventor: James E. Harper, 6804 Border Pl.,

Oxon Hill, Md. 20022 [22] Filed: Aug. 20, 1973 [21] Appl. No 389,563

Related US. Application Data [60] Continuation-impart of Ser. No. 250,297, May 4, 1972, abandoned, which is a division of Ser. No. 819,110, April 4, 1969, Pat. NO. 3,696,746.

Primary ExaminerDavid Klein Attorney, Agent, or FirmGardiner, Sixbey, Bradford and Carlson [5 7 ABSTRACT Non-ferrous lithographic printing plates, and especially those in which the hydrophobic image areas are constituted by photosensitive solvent soluble polymers, are made hydrophilic in non-image areas by application to the metal surface of the developed plate a fountain solution of an aqueous desensitizing solution comprising a phosphate glass such as sodium hexametaphosphate, about 75 300 grams per 1,000 cc of water, in admixture with a fluoride salt, such as sodium fluoride of about 20 150 grams per 1,000 cc of water, the admixed aqueous composition may be maintained at a pH in the range of pH 7 by a watersoluble acid, such as phosphoric acid since control of the pH in the fountain solutions can be critical with recent innovations in ink manufacture. The treatment can be performed at room temperature and in addition to cleaning the plate the fountain solution assists in preserving the hydrophilic areas of the printing plate during storage without special protection. Preferably in a press fountain the solution is diluted within the range of 1 part solution to 30 60 parts water.

2 Claims, No Drawings PROCESS FOR PRINTING WITH NON-FERROUS METAL LITHOGRAPI-IIC PRINTING PLATES PRIOR APPLICATION This application is a continuation-in-part of my prior application Ser. No. 250,297, filed May 4, 1972, now abandoned, which, in turn was a division of US. application Ser. No. 819,110, filed Apr. 4, 1969, now US. Pat. No. 3,696,746, issued Oct. 10, 1972, entitled DE- SENSITIZING NON-FERROUS LITHOGRAPHIC PRINTING PLATES WITH AQUEOUS PHOSPHATE GLASS COMPOSITIONS.

BACKGROUND OF INVENTION The photo-lithographic printing process, being planographic in character, (both printing and non-printing areas lie in the same plane) is, of necessity, a process of continual compromise. The plate, usually of aluminum or zinc, must be completely hydrophobic (grease acceptive, water repelling) in the printing areas and correspondingly hydrophilic (water acceptive and grease repelling) in the non-printing areas.

For many years the preparation of a lithographic plate has required a number of necessary processing steps to accomplish the twin objectives described above. In the earlier stages of the art, the surface of the sheet was uniformly roughened (grained) by placing it upon an oscillating table while covered with an abrasive slurry and a layer of glass or steel marbles for a period of several minutes. The grained plate was then washed, dried, and stored until ready for use. At the time of use the plate was usually counter-etched by extended immersion in a dilute acid solution, followed by a thorough scrubbing under running water with a soft bristle brush. Excess water was removed and the plate then subjected to a second protracted scrubbing, known as pre-etching" under a solution compounded from water, gum arabic, phosphoric acid, chrome alum, tannic acid, etc. In turn, the preetch composition was rinsed off and the plate made sensitive to light through application of a thin layer of an aqueous solution of egg albumin and ammonium or potassium bichromate which was then thoroughly dried in subdued light. After this preparation, a plate was ready for use in which it was exposed through a negative to a suitable ultra violet light source. After exposure, the areas exposed to the light became completely insolubilized to form a positive ink acceptive printing image on the plate. A thin layer of greasy developing ink was then applied to the entire plate surface and buffed dry. The areas which were not exposed to the light were then washed free of unexposed coating to bare the nonimage areas and excess moisture was removed. While still wet a thin desensitizing layer of the previously mentioned pre-etching solution was then applied to the plate and buffed dry. Plates so processed were then ready for the press and, from that time forward, the non-printing areas could not be permitted to dry without surface protection in the form of a manuallyapplied coating or film of an anti-oxidant. If, for any reason, a press stoppage occurred, the pressman was forced promptly to cover the plate with a thin film of acidified gum arabic to prevent surface oxidation. Despite this precaution, some non-image areas remained hydrophobic inducing a faint tinting called scumming or complete ink catchup. Despite the difficulties noted, the process described above is still in limited use today.

A major development in the art, some 20 years ago, subsequently eliminated much of the necessity for extreme care against oxidization of the surface of the base material. This development was the invention of the first commercially workable pre-sensitized offset plate in 1955. These plates consist of aluminum sheets of appropriate size and thickness, sheathed in an inert isolating layer of a hard, thin, insolubilized sodium silicate over their entire surface areas.

The silicate layers have been found to be completely compatible with both the aluminum base material and also with a class of light sensitive water soluble diazo sensitizers having reasonably good unexposed stability which enables the plates to be pre-prepared and stored for reasonably long periods of time.

The sodium silicate coatings also are hydrophilic in character and provide firm anchorage for the exposed diazo dyes with which the plates are sensitized. These hydrophilic silicate layers are applied to aluminum by extended immersion in hot solutions at temperature ranging from to 212 F.

However, while oxidation of the aluminum is prevented, the silicate areas inherently are spotty in that, in any given area, they may retain a greater or lesser degree of ink acceptivity. Thus, it is still necessary to continue the practice of laying down a thin film of acidified gum arabic or other desensitizing agent on the exposed and developed plate before it can be subjected to protracted periods of storage before or after usage. These gum arabic films provide protection only so long as they remain on the plate surface, since they form little if any chemical combination with the non-printing areas. Consequently, the protective coating is washed off by the pressman before beginning to print and is replaced by the pressman at the end of the press run if the plate is to be stored for possible future use.

With the rapid advance in polymer chemistry, it has been discovered that certain solvent soluble polymeric substances have light-sensitive properties equivalent to the diazos and thus hold out the possibility of being able to provide presensitized plates, i.e., ready for use plates, having a far more extended shelf life before use than the diazo presensitized plates discussed above. However, as is the case with almost every development, the advantages gained by the use of these stable lightsensitive polymers are offset by some disadvantages, not the least of which is the fact that such polymers, almost without exception, fail to adhere with any degree of consistency to hydrophilic substrates, in particular the silicate coated aluminum sheets noted above, after they have been exposed to light to insolubilize the image areas of the plate. In those instances where hydrophilic substrates have been employed much difficulty has been experienced by images walking of during normal printing operations. In those instances where satisfactory image anchorage has been obtained, success has been achieved by laying down the lightsensitive coating simultaneously with the cleaning and abrading of the aluminum surface without substrates of any kind. The reason that simultaneous surface preparation and coating does work is that the surface characteristics of aluminum change with great rapidity when exposed to air; the pure aluminum changing almost instantly to aluminum oxide. Hence, if any delay occurs between the cleaning and degreasing step which produces a relatively pure aluminum surface and the application of the light sensitive polymer to the pure surface,

the surface changes to the oxide before coating with the result that adherence of the light exposed coating to the surface is highly uncertain at best. In addition, plates made in accordance with the stated technique are still susceptible to the difficulties which arise from retention of ink in the non-printing areas just as were the old style plates having no protective coating. As a result it is still necessary to resort to the manual application of protective films during press stoppages, plate storage and the like. Also, and in passing, it should be noted that the so-called deep etch" plates, still widely used in fine color lithography, are subject to many of the same limitations in that they must be prepared by skilled technicians working with grained metal plates having no protective substrate of any kind.

In addition to the provision of silicate hydrophilic surfaces on aluminum plates, US Pat. No. 3,148,984, issued Sept. 15, 1964, also teaches that desirable results can be obtained in a coating process in which the surface of the photolithographic printing plate is first coated with an alkali metal phosphate glass-containing hydrophilic coating and then with an aqueous soluble light sensitive diazo resin. The alkali metal phosphate glass in that patent is applied by a treatment involving the use of elevated temperatures however. Thus, the process has no application in respect of imaged plates, i.e., developed plates ready for printing, because it has been found that the use of elevated temperatures in applying hydrophilic coatings causes degredation of the ink acceptive image areas.

Up to this point, the discussion has been directed primarily to preparation of the plate surface to protect the non-image hydrophilic areas during pre-use storage and also during the periods of non-use when the plates have been developed or imaged. There is another area also of great interest and that is the necessity of keeping the non-image or hydrophilic areas clean, which tend to pick up ink in these areas during press runs. The maintenance of surface cleanliness is accomplished by the fountain solution which is applied to the plate on the press during press runs to wet the non-image areas. Customarily, a solution or solutions containing acidic gum arabic are introduced into the press fountain and they are used in considerable amounts during printing in order to keep the non-printing areas clean. Here again, we have a cause and effect relationship in that while the non-image areas are kept clean, the acidic solutions tend to adversely affect the inks normally used, causing them to emulsify.

THE INVENTION In accordance with the invention, non-ferrous lithographic printing plates, and especially aluminum and zinc printing plates, are treated by application to the developed plate of an aqueous desensitizing solution comprising an alkali metal phosphate glass incorporated in the fountain solution. The phosphate glass may be used in combination with a buffer comprised of a fluoride salt, such as sodium fluoride, in an aqueous medium wherein the pH is maintained in the range of from pH 5 to approximately pH 7. These aqueous compositions react with the metal surface of the plate to provide a desensitizing action which takes place at room or moderate temperature so that the hydrophobic, ink acceptive image areas, which are preferably constituted by a light polymerized organic solventsoluble photosensitive polymers, remain undamaged by the surface treatment.

As explained in the prior issued patent, mentioned above, the plates are already provided with a phosphate coated or glassed surface. However, it must be realized that during the printing operation there is considerable friction generated between the surface of the plate and various instrumentalities in contact therewith, such as ink rollers, and particularly dampening rollers. This constantly repetitive friction has the effect of literally wearing the glassed surface much the same as an automobile tire wears against the road. Thus, if the surface is not replenished or protected, it will ultimately wear to the point of destruction and the quality of printing, which reduces in direct proportion to wear, would deteriorate to worthlessness as the non-image areas lose their hydrophilic properties and begin to pick up ink, either in faint blotches or, in a continuous film ruining the printed product. In any event, it is to be understood that the desensitizing or descumming action involves the active metal of the non-ferrous printing plate, e.g., the aluminum or zinc surface thereof and not the image areas which are hydrophilic and completely ink receptive and loaded" with greasy ink during printing.

Aside from the effect on the plate that occurs with the utilization of the aqueous treating solutions of the invention as a fountain solution, the solutions of the invention are particularly valuable since they can be employed under only very slightly acid conditions approaching neutrality and need not be utilized in large amounts. As a result, the solutions of the invention do not lead to the undesirable emulsification of the ink and consequential deterioration of printing quality which is characteristic of the more strongly acidic gum arabic-containing fountain solutions of the art.

Further, these gum arabic acid solutions cause rapid ink contamination of the surfaces of dampening rollers, forcing frequent and expensive replacement of their coverings. On the other hand, the solutions covered by this invention have permitted press operation for months at a time without dampening roller change.

Referring more particularly to the aqueous fountain compositions which are used in accordance with the invention, the prime ingredient is an alkali metal phosphate glass; it being appreciated that sodium is illustrative of the class of alkali metals and that potassium illustrates the other, and more usual, member of this well-known class of metals. The phosphate glass is constituted by a polyphosphate and this class of materials will be illustrated herein by sodium hexametaphosphate. It will be particularly understood that the hexametaphosphate glass may vary considerably with respect to the mol ratio of sodium to phosphorous and that all phosphate glasses are considered to be useful in the invention. The various useful glasses are further illustrated by such standard compositions as sodium hexametaphosphate, Grahams Salt, etc.

It is desired to point out that the phosphate glass can be used and may be preferable as the sole ingredient in the aqueous fountain solution on the press. The criteria for a given use of a particular composition of fountain solution is established by press conditions, in particular the type of ink being used for a given printing operation. Since some inks, even some press rolls are more sensitive to acid than others, the fountain solution used must be compatible with these ingredients and thus will be composed of an aqueous solution of phosphate glass having a neutral pH of 7 or a pH very close to neutrality. Even in the absence of further components, the phosphate glass represents an improvement over the use of gum arabic since the adverse effect of ink emulsification is largely avoided. On the other hand, unless further components are present in the aqueous solution, the desensitizing protection is temporary and washes off quite readily which is of more importance when the inventive compositions are used as set forth in U.S. Pat. No. 3,696,746 rather than as fountain solutions.

Insolubility in the invention can be achieved through the presence of a fluoride salt which may be constituted by any metal fluoride, preferably by an alkali metal or ammonium fluoride, and most preferably by the bifluoride. Thus, while sodium fluoride and bifluoride and like salts of ammonia or potassium are preferred, other fluoride salts such as calcium or magnesium fluoride may be used.

The preferred acids for providing a slightly acidic pH of from pH 5 to approximately pH 7, if an acidic solution is desired, are acids of phosphorus such as phosphoric acid, phosphorous acid or polyphosphorus acids.

Lastly, it can be helpful on occasion to include a wetting agent to assist in the wetting of the non-ferrous metal surface, but the particular nature of the wetting agent is of very secondary consideration. A polyoxyethylated nonylphenol containing from 9-30 mols of ethylene oxide per mol of nonylphenol illustrates the wetting agents which may be used as an optional component in the invention. Sodium lauryl sulfate will further illustrate the useful class of wetting agent which may be ionic or non-ionic. Generally, however, since the primary purpose of the fountain solution is to replenish the already desensitized nonimage areas which are hydrophilic and thus readily wettable so that no wetting agent is required in the fountain solution. With the use of some inks a wetting agent can result in emulsification so its usage calls for specific choices.

It is particularly desired that the aqueous compositions of the invention chemically react with the active metal surface and that this reaction take place at room or moderately elevated temperature to avoid degradation of the developed image areas on the plate and because of the expense and complications that would arise if temperature control of either the fountain solution or plate conditions were attempted on the press. It has been found under test conditions that the preferred compositions are capable of rapid reaction at approximately room temperature with the metal surface, e.g., aluminum. For this purpose, the concentration of the reagent is of significance. Thus, the aqueous solution should preferably contain from 75-300 grams of phosphate glass per 1,000 cc of water and from 20200 grams of fluoride salt per 1,000 cc of water. The reaction can take place in a few seconds up to several minutes and usually in from l seconds to minutes. As one might suspect, the rapidity of the reaction increases as the pH decreases within the range set forth. If the pH is too low, then pin holes and spottiness develop. On the other hand, as soon as the pH becomes even slightly alkaline, the reaction is greatly slowed. The speed of reaction also increases with increasing concentration and temperature. Obviously, a similar reaction is taking place on the press. However, since the plate is continually wet with fountain solution, the speed of the reaction is not as critical as in the case of plate desensitization, hence the pH of the solution can approach neutrality without significant adverse effect on either the desired reaction or on the ink or press parts which come in contact with the fountain solution.

While it has been stated that no provision need be made for temperature control it should be realized that the normal conditions surrounding the press are usually quite warm. Since the reaction can take place at average room temperature and is speeded up with increases in solution temperature, provided the temperature does not exceed F. where degradation of the image areas can occur, the inherent warm conditions around the press are quite favorable for the reaction between the plate surface and fountain solution despite the fact that the fountain solution is at near neutral pH or at best very, very slightly on the acidic side certainly no greater than a pH of 5 where an acid salt is included in the solution.

The following examples are illustrative of the invention:

EXAMPLE 1 The listed chemicals were mixed in the proportions shown, then cooled to room temperature, then diluted with water from 30 to 60 parts for press operation:

*optional A recently developed clean, new, aluminum based phosphate glassed plate glassed after development was put on a lithographic press. The above compounded solution was introduced into the press fountain system in dilute form, approximately 1 part solution to 30 parts water. The press was inked in normal fashion and run in normal fashion.

The entire press run was completed without any evidence of scumming or catch-up in the non-image areas of the plate. There was no contamination of dampening rollers. Thereafter the press was deliberately shut down with the plate intact for 4 hours. At the end of this 4- hour period the press was started again and the dampening rollers dropped on the surface of the plate. The first few impressions from the plate showed a minimal amount of toning. Still without change, the run was continued and by the twentieth impression, the nonimage areas were absolutely clean and the image was as clear and sharp as in the first press run.

The same conditions were repeated but the fountain solution was changed to a standard gum arabic solution and the plate, unglassed but desensitized by conventional means, was used.

The conditions of the press run were repeated. Toward the tail end of the press run it was quite evident that the plate was beginning to deteriorate because the image lost some of its sharpness and there was noticeable toning in non-image areas.

Again the press was stopped and the plate left standing unattended for only ten minutes after which the press was restarted. The plate rolled up completely EXAMPLE 2 The listed chemicals were mixed, cooled and bottled:

Formula 1 Formula 2 Water (l50 F.) 1,000 cc 1,000 cc Sodium Hexametaphosphate 100 gm 200 gm Sodium Bifluoride NaF.HF.l. 100 gm 200 gm *Phosphoric Acid 20 gm 40 gm Polyoxyethylated Nonylphenol 4 gm 4 gm *optional EXAMPLE 3 The listed chemicals were mixed, cooled and bottled:

Formula 1 Formula 2 Water 150 F.) 1,000 cc 1,000 cc Sodium Hexametaphosphate 100 gm 200 gm Ammonium Bifluoride (NH F. HF) 40 gm 80 gm *Phosphoric Acid 20 gm 40 gm *Polyoxyethylated Nonylphenol 4 gm 4 gm *optional EXAMPLE 4 The listed chemicals were mixed, cooled, and bottled:

Formula 1 Formula 2 Water (150 F.) 1,000 cc 1,000 cc Sodium Hexametaphosphate lOO grn 200 gm Potassium Fluoride (KF) 40 gm 80 gm *Phosphoric Acid 20 gm 40 gm *Polyoxyethylated Nonylphenol 4 gm 4 gm *optional EXAMPLE 5 The listed chemicals were mixed, cooled and bottled:

Formula 1 Formula 2 Water (150 F.) 1,000 cc 1,000 cc Sodium Hexametaphosphate 100 gm 200 gm Calcium Fluoride (CaF 40 gm 80 gm *Phosphoric Acid 20 gm 40 gm *Polyoxyethylated Nonylphenol 4 gm 4 gm *optional Each of the formulae in Examples 2 through 5 were diluted by the addition of 30 to 60 parts of water before use in press fountains.

As a final check, the plates used in the press tests in the above described examples were removed from the press, swabbed with the undiluted solution employed in the example under test, dried down and stored. Approximately 120 days later each plate was placed on the press, dampened with a pad wet with fountain solution and copy was run. Excellent results were obtained from the plates used in all examples in that the previous print quality was maintained.

While all of the above examples produced satisfactory results as regards the desensitizing function, it was noted that on occasion there was an unusual emulsification of the ink and some evidence of roll stripping on the press. It was also noted that some of the metallic fluorides did not perform as well as others. For example, fountain solutions compounded with sodium bifluoride displayed a much greater tendency toward roll stripping than did fountain solutions containing sodium fluoride.

Consequently, further experimental runs were conducted with variations in the compounding of the various fountain solutions. The procedure for preparation was as follows:

Sodium phosphate compounds are in powdered or granular form and are added to water heated to 125 to 140 F. while the water is under violent agitation.

After 5-10 minutes of agitation the phosphate is usually completely in solution.

Thereafter the metallic fluoride also in powder form is added to the phosphate solution which again is agitated to obtain a complete solution.

Thereafter, the acid, if used, preferably an percent concentrated solution, is added to the solution along with a wetting agent such as Alipal CA630, manufactured by General Analine and Film Corp. A coloring agent such as Rit Instant All Purpose Liquid Dye may be added.

The solution is then diluted with 1 part solution to thirty to sixty parts water and is ready for use. Where the solution is not to be used immediately, it can be bottled for future use and diluted with 1 part solution to 30 60 parts water at the time of use.

The following examples produced satisfactory results:

Example 6 Sodium **Phos- Hexameta- *Sodium phoric Alipal phosphate Bifluoride Acid CA-630 Water grams 100 20 grams 4 grams 1,000 cc grams 10 lbs 10 lbs 2 lbs 6 oz 12 gallons 100 lbs 25 lbs 20 lbs 3.75 lbs gallons Example 7 50 grams 20 grams 10 grams 4 grams 1,000 cc 5 lbs 2 lbs lb 6 oz 12 gallons 5() lbs 20 lbs 10 lbs 3.75 lbs 120 gallons *(NaFJ-lF) optional Example 8 Sodium **Phos- Hexameta- *Ammophoric Alipal nium phosphate Bifluoride Acid CA630 Water 100 grams 40 grams 20 grams 4 grams 1,000 cc 10 lbs 4 lbs 2 lbs 6 oz 12 gallons 100 lbs 40 lbs 20 lbs 3.75 lbs 120 gallons *(NH FHF) optional Example 8 Continued Sodium **Phos Hexameta- *Sodium phoric Alipal phosphate Bifluoride Acid (A-630 Water Example 9 Sodium **Phos- Hexameta- *Potasphoric Alipal sium phosphate Fluoride Acid CA630 Water 100 grams 40 grams 20 grams 4 grams 1,000 cc l lbs 4 lbs 2 lbs 6 02 I2 gallons 100 lbs 40 lbs 20 lbs 3.75 lbs 120 gallons Z) optional As a result of all of the noted tests, it was concluded that an excellent general norm for fountain solutions evolved from the basic combination of five parts sodium hexametaphosphate; two parts sodium fluoride and one hundred parts water Results produced by using this formulation as a norm were generally excellent under most press conditions and with most inks presently in use. Fountain solutions prepared in accordance with this general formulation are in almost neutral to only slightly acidic range having a pH of from pH to pH 7 which alleviates the problem of ink emulsification.

On occasion, however, it has been found that due to peculiar press conditions there is some difficulty experienced with stripping or emulsification, and it has been found that adjustment of the pH by empirical test during addition of phosphoric acid to a pH of 5 and the reduction of the ratio of sodium fluoride down to zero will give satisfactory results.

Having thus described the invention, it will be obvious that modifications and variations, falling within the scope of the claims, will occur to those skilled in the art, wherein what is claimed is:

l. A process for treatment of a non-ferrous lithographic printing plate in a planographic printing process comprising applying to said printing plate a fountain solution containing an alkali metal phosphate glass in the proportion of from 50-300 grams of a said alkali metal phosphate glass to 1,000 cc of water, said solution containing an acid of phosporous to provide a pH of from 5 to 7; said solution being diluted in the ratio of 1 part solution to 30 to 60 parts of water when introduced into the press fountain.

2. A process for treatment of a nonferrous alkali metal printing plate in a planographic printing process comprising applying to said printing plate a fountain solution containing from about to 300 grams of an alkali metal phosphate glass per 1,000 cc of water and from about 20-l50 grams of a fluoride salt per 1,000 cc of water, said solution containing an acid of phosporous to provide a pH of from 5 to 7; said solution being further diluted in the range of from 1 part solution to 30-60 parts water when introduced in the fountain of the press. 

1. A PROCESS FOR TREATMENT OF A NON-FERROUS LITHOGRAPHIC PRINTING PLATE IN A PLANOGRAPHIC PRINTING PROCESS COMPRISING APPLYING TO SAID PRINTING PLATE A FOUNTAIN SOLUTION CONTAINING AN ALKALI METAL PHOSPHATE GLASS IN THE PROPORTION OF FROM 50-300 GRAMS OF A SAID ALKALI METAL PHOSPHATE GLASS TO 1,000 CC OF WATER, SAID SOLUTION CONTAINING AN ACID OF PHOSPOROUS TO PROVIDE A PH OF FROM 5 TO 7; SAID SOLUTION BEING DILUTED IN THE RATIO OF 1 PART SOLUTION TO 30 TO 60 PARTS OF WATER WHEN INTRODUCED INTO THE PRESS FOUNTAIN.
 2. A process for treatment of a non-ferrous alkali metal printing plate in a planographic printing process comprising applying to said printing plate a fountain solution containing from about 75 to 300 grams of an alkali metal phosphate glass per 1,000 cc of water and from about 20-150 grams of a fluoride salt per 1,000 cc of water, said solution containing an acid of phosporous to provide a pH of from 5 to 7; said solution being further diluted in the range of from 1 part solution to 30-60 parts water when introduced in the fountain of the press. 